1. Field of the Invention
This invention relates to a charging member and an electrophotographic apparatus.
2. Description of the Related Art
In order to provide an electrical conductivity of approximately from 1×103 to 1×107 Ω·cm in volume resistivity to an elastic-material layer of a charging roller used in a contact charging system, it is known to form the elastic-material layer by using an electro-conductivity type conductive rubber composition compounded with electrically conductive particles such as carbon black. However, such an elastic-material layer has, as disclosed in Japanese Patent Application Laid-open No. 2007-292298, a problem that its electrical resistance heavily depends on the state of dispersion of the electrically conductive particles, and therefore electrical resistance non-uniformity in the charging roller may become large. Also, there is a case that in the charging member having such an elastic-material layer, an aggregation of the electrically conductive particles in the elastic-material layer is accelerated by the continuous application of direct-current voltage, and electrical resistance of the elastic-material layer is changed over time. Then, Japanese Patent Application Laid-open No. 2007-292298 discloses that it is attempted to resolve such a problem by employing the step of dispersing the electrically conductive particles in a conductive coat layer forming material by agitating these by means of a bead mill.